Detectives investigating the murder of Bob Woolmer yesterday said they were decoding crucial CCTV footage which could reveal the identity of the Pakistan coach's killer. Mark Shields, the former Scotland Yard superintendent who is No 2 in the Jamaican police force, said the new material was "critically important, because it may give us an image of the killer or killers".

The development came as the police defended their decision to let the Pakistan team fly home, via London.

Officers have begun to examine the CCTV footage, which has been digitalised. Mr Shields said he was optimistic that the quality of the pictures would be good enough to help determine who was present on the 12th floor of the Pegasus hotel in Kingston between 8.30pm on Saturday, March 17, when Woolmer was last seen, and 10.45am on the Sunday, when a chambermaid found him lying lifeless in the bathroom. The film could also help to determine a precise time of death.

The CCTV cameras would have filmed anyone leaving or entering the lifts on Woolmer's floor of the 17-storey hotel, as well as anyone using the back service entry. However, there are no cameras along the corridor, which means that movement between rooms on the floor would be undetected.

As the Pakistan team left, having been knocked out of the World Cup, Mr Shields said he was powerless to keep the team in Jamaica. To do so "would have been to use a sledgehammer to crack a nut. It would probably have caused a significant diplomatic incident and had an extremely adverse effect on the World Cup". There was insufficient evidence to hold anyone as a suspect at this time.

With speculation continuing to swirl around the relationship between Woolmer and players in the team, the squad began a two-day stopover in London before their return to Islamabad. At the Holiday Inn near Heathrow airport, the team's media manager, Pervez Jamil Mir, complained that the team was being kept in the dark on the police inquiry, but said he expected to be able to make a statement today. He said: "We still haven't been told officially in writing by the police how Mr Woolmer was murdered. We want the police to tell us what is going on."

He said he had not been asked by the police to make any arrangements should the players be recalled to Jamaica. He added: "If the police want players for any further questioning, they are here to answer them."

The murder hunt will now spread its net to other squads whose members were at the Pegasus hotel on the Sunday morning that Woolmer was found strangled in room 374. Brian Lara, the West Indies captain, has been questioned and all members of the West Indies and Ireland teams will be asked to volunteer a statement, fingerprints and a DNA swab.

Several top managers and players from the Pakistan, West Indies and Ireland teams were staying on the 12th floor, including Mr Lara, the Ireland captain Trent Johnson, Murray Stevenson, the Pakistan fitness trainer, Darren Lifson, another team manager, and the Pakistan player Danish Kaneria.

Inzamam-ul-Haq, the Pakistan captain, was also on the 12th floor until shortly before Woolmer's murder, when he moved to the 5th floor. He was questioned by police on Saturday about why he had changed rooms and told them he had wanted to be closer to the other players.

Talat Ali, the team manager, and Mushtaq Ahmed, its bowling coach, were also questioned to fill in holes in their earlier statements, police said.

Pakistan has asked to send a detective to Jamaica to investigate what it claims were links between an Indian bookmaker and the murder. A senior government official told the Guardian that two Pakistan players told Jamaican police that Woolmer had a blazing argument with a bookmaker based in Mumbai on Saturday night. "Bob Woolmer said he had just thrown a bookie out of his room. He didn't give any reasons," the official said.

Mr Shields said he was unaware of any bookmakers having stayed at the Pegasus, or any suggestions of Indian involvement. Indian cricket officials also dismissed the allegations as "speculation and stories".

Two Pakistani diplomats from Washington are now based in Kingston to act as liaison between the government and the police, and were yesterday given a tour of the crime scene.

The widening of the investigation means it could now enter a prolonged phase with no obvious signs of a breakthrough. Mr Shields warned against easy fixes: "There is always a tendency to think a murder investigation can be solved in 45 minutes, as it is on TV. It isn't like that."

Though he stressed that no member of the Pakistan team was under suspicion, he said he was in discussion with the diplomats about what would happen were he to want any individuals to return to Jamaica. He added that he would "cross that bridge when we come to it". There is no extradition treaty between the two countries.

In 1996 Pakistan returned a youth cricketer, Zeeshan Pervez, to Jamaica to face charges that he had raped a woman in a Kingston hotel. He was acquitted.

The rumour mill: who killed the coach?

A row within the Pakistan team

There has been speculation for several days about a row between Woolmer and one or more of his players on the team coach on the way back from last Saturday's defeat by Ireland. Mark Shields, leading the investigation, said yesterday that he had questioned security officers on the bus and that while the mood had been "sombre" there was no evidence of any argument.

Match-fixing

Two Jamaican detectives have been assigned to work with the anti-corruption unit of the International Cricket Council. Experts in gambling fraud say it is unlikely a whole match would have been thrown, though the defeat to Ireland raised that suspicion. The spokesman for the Pakistan team, Pervez Mir, has said Woolmer was upset before the tour because he thought he had lost the manuscript of a book he was writing - a detail that prompted speculation that he was poised to blow the lid on match-fixing. Mr Shields dismissed the theory, saying the manuscript focused solely on fitness in the sport.

Plot by Indian bookmakers

The Pakistan government yesterday floated to the Guardian the idea that Indian betting syndicates were involved in the murder, citing what two Pakistan players told Jamaican police when questioned on Thursday. A senior official said three bookies had checked into the Pegasus hotel before the start of the World Cup. The Pakistan players told police that Woolmer had thrown one of the bookies out of his room shortly before his murder, the official said. But this theory was denied by Indian cricket officials, and treated sceptically by senior Jamaican detectives.

Expert assassination

The absence of any signs of a struggle between Woolmer and his attacker has prompted the theory that this was a professional job. However, Mr Shields has said the idea of a paid assassin is not being pursued, and that it is much more likely that Woolmer knew his attacker.

Drugging or poisoning

Detectives are waiting for the results of toxicology and histology tests on samples from Woolmer's body which would show whether he had been drugged or poisoned before being strangled. It is known that the coach ordered room service on Saturday night.

Disgruntled fan

Those familiar with international cricket say it is not uncommon for the doors of managers to be left open as players come in after a game to talk through the events of the day. Woolmer is known to have kept himself very accessible to his team. It is possible to go up in the lift with other hotel guests, and there is a stairwell at the back of the hotel which gives access to all floors. Emotions among Pakistan fans ran high after the humiliating defeat by Ireland, with extraordinary scenes witnessed in Pakistan.Ed PilkingtonDeclan Walsh